Lymphatic system and body defenses Nonspecific defenses Do not distinguish one type of threat from another 7 types Specific defenses Protect against particular threats Depend upon the activation of lymphocytes

SECTION 22-3 Nonspecific Defenses

Nonspecific Defenses, Physical barriers Keep hazardous organisms outside the body Includes hair, epithelia, secretions of integumentary and digestive systems

Figure 22.10 Nonspecific Defenses (Part 1 - Physical Barriers)

Nonspecific Defenses, Phagocytes Remove cellular debris and respond to invasion by foreign pathogens Monocyte-macrophage system - Fixed and free Microphages – Neutrophils and eosinophils Move by diapedesis Exhibit chemotaxis

Figure 22.10 Nonspecific Defenses (Part 2 - Phagocytes)

Nonspecific Defenses, Immunological surveillance Constant monitoring of normal tissue by NK cells NK cells Recognize cell surface markers on foreign cells Destroy cells with foreign antigens

NK cell activation Recognition of unusual surface proteins Rotation of the Golgi toward the target cell and production of perforins Release of perforins by exocytosis Interaction of perforins causing cell lysis

Figure 22.10 Nonspecific Defenses (Part 3 - Immunological Surveillance)

Figure 22.11 How Natural Killer Cells Kill Cellular Targets

Nonspecific Defenses, Interferons (cytokines) Small proteins released by virally infected cells Trigger the production of antiviral proteins Three major types of interferons are: Alpha– produced by leukocytes and attract/stimulate NK cells Beta– secreted by fibroblasts causing slow inflammation Gamma – secreted by T cells and NK cells stimulate macrophage activity

Figure 22.10 Nonspecific Defenses (Part 4 - Interferons)

Nonspecific Defenses, Complement system Cascade of ~11 plasma complement proteins (C) Destroy target cell membranes Stimulate inflammation Attract phagocytes Enhance phagocytosis

Complement proteins interact with on another via two pathways Classical Alternative

Figure 22.10 Nonspecific Defenses (Part 5 - Complement System)

Figure 22.12 Complement Activation

Nonspecific Defenses, Inflammation Localized tissue response to injury producing Swelling Redness Heat Pain Effects of inflammation include Temporary repair of injury Slowing the spread of pathogens Mobilization of local, regional, and systemic defenses

Figure 22.10 Nonspecific Defenses (Part 6 - Inflammatory Response)

Figure 22.13 Inflammation Figure 22.13

Nonspecific Defenses, Fever Maintenance of a body temperature above 37.2oC (99oF) Pyrogens reset the hypothalamic thermostat and raise body temperature Pathogens, toxins, antigen-antibody complexes can act as pyrogens

Figure 22.10 Nonspecific Defenses (Part 7 - Fever)

SECTION 22-4 Specific Defenses

Forms of immunity Innate immunity Genetically determined Present at birth Acquired immunity Not present at birth Achieved by exposure to antigen Active immunity Passive immunity

Figure 22.14 Types of Immunity

Properties of immunity Specificity – activated by and responds to a specific antigen Versatility – is ready to confront any antigen at any time Memory – “remembers” any antigen it has encountered Tolerance – responds to foreign substances but ignores normal tissues

The immune system response Antigen triggers an immune response Activates T cells and B cells T cells are activated after phagocytes exposed to antigen T cells attack the antigen and stimulate B cells Activated B cells mature and produce antibody Antibody attacks antigen

Figure 22.15 An Overview of the Immune Response

SECTION 22-5 T cells and Cell-mediated Immunity

Major types of T cells Cytotoxic T cells (TC) – attack foreign cells Helper T cells (TH) – activate other T cells and B cells Suppressor T cells (TS) – inhibit the activation of T and B cells

Antigen presentation Antigen-glycoprotein combination appears on a cell membrane Called MHC proteins (Major Histocompatibility Complex) Coded for by genes of the MHC T-cells sensitive to the antigen are activated upon contact

MHC classes Class I – found on all nucleated cells Class II – found on antigen presenting cells and lymphocytes

Lymphocytes respond to antigens bound to either class I or class II MHC proteins Antigen recognition T cell membranes contain CD markers CD3 markers present on all T cells CD8 markers on cytotoxic and suppressor T cells CD4 markers on helper T cells

Figure 22.16 Antigens and MHC Proteins

Figure 22.16 Antigens and MHC Proteins

Figure 22.16 Antigens and MHC Proteins Figure 22.16b

Activation of CD8 cells Responds quickly giving rise to other T cells Cytotoxic T cells – seek out and destroy abnormal cells lymphotoxin Memory TC cells – function during a second exposure to antigen Suppressor T cells – suppress the immune response

Figure 22.17 Antigen Recognition and the Activation of Cytotoxic T Cells

Figure 22.17 Antigen Recognition and the Activation of Cytotoxic T Cells PLAY Animation: Cytotoxic T Cell Activation Figure 22.17

Activation of CD4 T cells by antigens presented on class II MHC proteins Produces helper T cells and memory T cells Activated helper T cells Secrete lymphokines that coordinate specific and nonspecific defenses Enhance nonspecific defenses Stimulate the activity of NK cells Promote activation of B cells

Figure 22.18 Antigen Recognition and Activation of Helper T cells PLAY Animation: Antigen Recognition and Helper T Cell Activation Figure 22.18

Figure 22.19 A Summary of the Pathways of T Cell Activation

The Lymphatic System and Immunity Chapter 22, part 4 The Lymphatic System and Immunity

SECTION 22-6 B Cells and Antibody-mediated Immunity

B cell sensitization of activation Sensitization – the binding of antigens to the B cell membrane antibodies Antigens then displayed on B cell Class II MHC TH cells activated by same antigen stimulate B cell Active B cell differentiates into Memory B Cell or Plasma cell Plasma cells synthesize and release antibody

Figure 22.20 The Sensitization and Activation of B Cells PLAY Animation: B Cells and Antibody Production Figure 22.20

Antibodies structure Antibodies are Y-shaped proteins consisting of: Two parallel polypeptide chains Heavy chains and light chains Constant region and variable region Antigen binding site

Figure 22.21 Antibody Structure

Figure 22.21 Antibody Structure

Figure 22.21 Antibody Structure Figure 22.21b-d

Actions of antibodies include: Neutralization Agglutination and precipitation Activation of complement Attraction of phagocytes Opsinization Stimulation of inflammation Prevention of adhesion

Classes of Antibodies (immunoglobins) IgG – resistance against many viruses, bacteria and bacterial toxins IgE – accelerates local inflammation IgD – found on the surface of B cells IgM – first type secreted after antigen arrives IgA – primarily found in glandular sec

Primary and secondary antibody response Primary response Takes about two weeks to develop Produced by plasma cells Secondary response Rapid increase in IgG Maximum antibody titer app

Figure 22.22 The Primary and Secondary Immune Responses

Figure 22.23 An Integrated Summary of the Immune Response

Figure 22.25 The Course of the Body’s Response to Bacterial Infection Figure 22.25a, b

SECTION 22-7 Normal and Abnormal Resistance

Development of the Immune Response Immunological competence The ability to demonstrate an immune response after exposure to an antigen Fetuses receive immunity from the maternal bloodstream Infants acquire immunity following exposure

Immune disorders Autoimmune disorders Immune response mistakenly targets normal cells Immunodeficiency diseases Immune system does not develop properly or is blocked

Allergies Inappropriate or excessive immune response to allergens Anaphylaxis Circulating allergen affects mast cells throughout body

Figure 22.26 The Mechanism of Anaphylaxis

Stress and the immune response Interleukin-1 released by active macrophages Triggers release of ACTH resulting in glucocorticoid release Moderates the immune response Lowers resistance to disease

Stress can cause the following: Depression of the inflammatory response Phagocytic reduction Inhibition of interleukin secretion

You should now be familiar with: The structure and function of lymphatic cells, tissues and organs The body’s nonspecific defenses and the components and mechanisms of each Specific resistance, cell-mediated immunity and antibody mediated immunity The role of the T cell, B cell and antibodies in specific immunity